Here’s yet another reason to really pay attention to nourishing your body while you fight cancer or try to prevent it: As much as 70 percent of your immune system is in and around your gastrointestinal tract. If you take care of your gut, your immune function will grow stronger. And that will help you resist all kinds of diseases, including cancer.

Certain foods, like apples, also promote fermentation benefits similar to what probiotics offer. You’re surely familiar with the saying, “An apple a day keeps the doctor away.” That’s because the skin of an apple has a lot of fiber, or pectin. Pectin is fermented in your intestines and produces short-chain fatty acids. These acids keep harmful bacteria at bay. They also nourish the cells that line your intestines, making them stronger and more cancer-resistant.